The present invention relates generally to electrified trains and more specifically to a method and apparatus for connecting a power source to an energized power line of the train.
Electro-pneumatic train braking requires electrical current to be transmitted over wires, serially connected between each car over the entire length of the train or consist from the locomotive. A typical electro-pneumatic (EP) brake system requires from 1200 watts to 2500 watts of power operating at voltages in the range of 230 volts DC.
In trains of substantial length, for example, freight trains, which may extend for a mile and a half to two miles and includes over one hundred cars, there exists a need to provide power sources other than the one at the head locomotive to maintain the current and voltage levels along the trainline. The composition of the train varies continuously. The proposed use of hermaphroditic connectors between the cars increases the changes of polarity reversals throughout the length of the trainline. While this has not caused a problem with respect to any of the equipment on the individual cars, it would cause a problem if additional power sources were connected to the trainline without knowing the appropriate polarity of the trainlines.
The present invention provides a method and apparatus for addressing this problem. The method includes using a local power controller in the trainline to determine the polarity of the power lines which run through the trainline. The local power controller then connects the second power source to the power lines with the determined polarity. Finally, the local power controller powers the power lines with a second power source once the connection of the appropriate polarity has been made.
A master controller, preferably at the locomotive, transmits a power command to the local power controller to initiate determining the polarity, connecting the proper output lines, and applying power to the trainline. The power command is transmitted over the trainlines and preferably over the power lines. To determine the polarity, the local controller places parallel, opposed diodes across the power lines and determines conduction of one of the diodes. This will indicate the polarity of the lines. The local power controller uses a switch to place the diodes across the power lines and the switch may be either relay or transistor switches. The local power controller determines conduction of the diode through an electro-optic isolator. The local power controller also uses a switch to connect the second power source to the power lines with the determined polarity. If the power lines have no polarity, the local power controller connects the second power source to the power lines with a default polarity. The switch may be a relay controlling two sets of form C contacts or may be transistor switches. The local power controller also uses a switch to control the powering of the power lines with the second power source.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.